Method, base station, UE, and system for sending and receiving PDCCH signaling

ABSTRACT

A method, a base station, a User Equipment (UE) and a system for sending and receiving Physical Downlink Control Channel (PDCCH) signaling are disclosed. A method includes determining locations of a first search space and a second search space of a User Equipment (UE). A method also includes sending PDCCH signaling with no Carrier Indication Field (CIF) to the UE in a physically overlapped region between the first search space and the second search space if the physically overlapped region exists and a length of the PDCCH signaling with no CIF in the first search space is equal to a length of PDCCH signaling with the CIF in the second search space.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/685,092, filed on Nov. 26, 2012, which is a continuation of U.S.application Ser. No. 13/336,209, filed on Dec. 23, 2011. The U.S.application Ser. No. 13/336,209 is a continuation of InternationalApplication No. PCT/CN2011/070937, filed Feb. 11, 2011. TheInternational Application claims priority to Chinese Patent ApplicationNo. 201010111643.5, filed on Feb. 11, 2010, Chinese Patent ApplicationNo. 201010142160.1, filed on Mar. 29, 2010, and Chinese PatentApplication No. 201010165438.7, filed on Apr. 30, 2010. All of theseapplications are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

The present invention relates to communications technologies, and inparticular, to a method, a base station, a User Equipment (US), and asystem for sending and receiving Physical Downlink Control Channel(PDCCH) signaling.

BACKGROUND

A Carrier Aggregation (CA) technology is introduced in a Long TermEvolution-Advanced (LTE-A) system. That is, multiple Component Carriers(CC) are scheduled for one UE to fulfill a higher peak rate and servicerequirements.

In a system not based on the CA technology, resources of only onecarrier can be scheduled by a piece of Physical Downlink Control Channel(PDCCH) signaling. In a system based on the CA technology, if a UEaggregates multiple carriers to transmit data, the UE requires multiplepieces of corresponding PDCCH signaling.

In an LTE-A system, resources can be scheduled in two modes. One mode isSame-CC Scheduling (SCS), which means that the PDCCH signaling on acarrier may be used to schedule only resources of this carrier and theuplink carrier corresponding to this carrier; the other mode is Cross-CCScheduling (CCS), which means that the PDCCH signaling on a carrier maybe used to schedule the resources of this carrier or other carriers. InCCS mode, a Carrier Indicator Field (CIF) needs to be added toUE-specific PDCCH signaling to indicate resources of which carrier arecurrently scheduled by the PDCCH signaling. Specially, no CIF is addedto PDCCH signaling shared by multiple UEs so that the UEs in an LTE-Asystem and the UEs in an LTE system can coexist.

The base station sends semi-static Radio Resource Control (RRC)signaling to the UE, indicating whether the resource scheduling modecurrently applied by the UE is CCS or SCS. When the UE uses the SCS modeto schedule resources in the RRC-idle state or the RRC-connected state,the PDCCH signaling includes no CIF. When the UE uses the CCS mode toschedule resources in the connected state, the PDCCH signaling includesa CIF. After the base station sends the semi-static RRC signaling to theUE, if the UE receives the semi-static RRC signaling, the UE detects andparses the PDCCH signaling according to the resource scheduling modeindicated in the semi-static RRC signaling. However, after the basestation sends the semi-static RRC signaling, the base station is notsure whether the UE has received the semi-static RRC signaling correctlyuntil the base station receives RRC Connection Reconfiguration Completesignaling (RRC Connection Reconfiguration Complete signaling) returnedby the UE, and the scheduling on the base station is uncertain in theperiod from sending the semi-static RRC signaling to receiving the RRCConnection Reconfiguration Complete signaling.

The following problems exist in the prior art. The scheduling on thebase station is uncertain in the period from sending the semi-static RRCsignaling to receiving the RRC Connection Reconfiguration Completesignaling returned by the UE, which causes the UE to parse the signalingincorrectly.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a method, a base station, aUE, and a system for sending PDCCH signaling to overcome schedulinguncertainty on the base station.

Embodiments of the present invention provide a method, a base station, aUE, and a system for receiving PDCCH signaling to prevent the UE fromparsing the PDCCH signaling incorrectly.

A method for sending PDCCH signaling according to an embodiment of thepresent invention includes determining locations of a first search spaceand a second search space of a UE; and sending only PDCCH signaling withno CIF to the UE in a physically overlapped region between the firstsearch space and the second search space if the physically overlappedregion exists and a length of the PDCCH signaling with no CIF in thefirst search space is equal to a length of PDCCH signaling with the CIFin the second search space.

Another method for sending PDCCH signaling according to an embodiment ofthe present invention includes determining locations of a first searchspace and a second search space of a UE; and sending only PDCCHsignaling with a CIF to the UE in a physically overlapped region betweenthe first search space and the second search space after receiving RRCConnection Reconfiguration Complete signaling sent by the UE if thephysically overlapped region exists and a length of PDCCH signaling withno CIF in the first search space is equal to a length of the PDCCHsignaling with the CIF in the second search space.

Another method for sending PDCCH signaling according to an embodiment ofthe present invention includes determining locations of a first searchspace and a second search space of a UE; and sending third PDCCHsignaling or fourth PDCCH signaling to the UE in a physically overlappedregion between the first search space and the second search space withina time interval from sending RRC signaling to the UE to receiving RRCConnection Reconfiguration Complete signaling returned by the UE. Thethird PDCCH signaling is PDCCH signaling with no Carrier IndicationField (CIF) and the fourth PDCCH signaling is PDCCH signaling with theCIF if a length of first PDCCH signaling in the first search space isequal to a length of second PDCCH signaling in the second search spaceand the physically overlapped region exists. The first PDCCH signalingis PDCCH signaling with no CIF, the second PDCCH signaling is PDCCHsignaling with the CIF, a length of the third PDCCH signaling is unequalto a length of the fourth PDCCH signaling, the length of the third PDCCHsignaling is different from the length of the first PDCCH signaling, andthe length of the fourth PDCCH signaling is different from the length ofthe first PDCCH signaling.

A method for receiving PDCCH signaling according to an embodiment of thepresent invention includes receiving only PDCCH signaling with no CIF ina physically overlapped region between a first search space and a secondsearch space and parsing the PDCCH signaling with no CIF according toonly a set rule of parsing PDCCH signaling with no CIF if the physicallyoverlapped region exists and a length of the PDCCH signaling with no CIFin the first search space of a UE is equal to a length of PDCCHsignaling with the CIF in the second search space of the UE.

Another method for receiving PDCCH signaling according to an embodimentof the present invention includes receiving PDCCH signaling with a CIFin a physically overlapped region between a first search space and asecond search space after a UE parses RRC signaling from a base stationcorrectly, and parsing the PDCCH signaling with the CIF according toonly a set rule of parsing PDCCH signaling with the CIF if thephysically overlapped region exists and a length of PDCCH signaling withno CIF in the first search space of the UE is equal to a length of thePDCCH signaling with the CIF in the second search space of the UE.

A base station according to an embodiment of the present inventionincludes a first determining module that is configured to determinelocations of a first search space and a second search space of a UE. Afirst sending module is configured to send only PDCCH signaling with noCIF to the UE in a physically overlapped region between the first searchspace and the second search space if the physically overlapped regionexists and a length of the PDCCH signaling with no CIF in the firstsearch space is equal to a length of PDCCH signaling with the CIF in thesecond search space after the first determining module determines thelocations of the first search space and second search space of the UE.

Another base station according to an embodiment of the present inventionincludes a second determining module that is configured to determinelocations of a first search space and a second search space of a UE. Asecond sending module is configured to send third PDCCH signaling orfourth PDCCH signaling to the UE in a physically overlapped regionbetween the first search space and the second search space within a timeinterval from sending RRC signaling to the UE to receiving RRCConnection Reconfiguration Complete signaling returned by the UE afterthe first determining module determines the locations of the firstsearch space and the second search space of the UE. The third PDCCHsignaling is PDCCH signaling with no CIF and the fourth PDCCH signalingis PDCCH signaling with the CIF if a length of first PDCCH signaling inthe first search space is equal to a length of second PDCCH signaling inthe second search space, where the first PDCCH signaling is PDCCHsignaling with no CIF and the second PDCCH signaling is PDCCH signalingwith the CIF, and a length of the third PDCCH signaling is unequal to alength of the fourth PDCCH signaling, and the length of the third PDCCHsignaling is different from the length of the first PDCCH signaling, andthe length of the fourth PDCCH signaling is different from the length ofthe first PDCCH signaling.

Another base station according to an embodiment of the present inventionincludes a third determining module that is configured to determinelocations of a first search space and a second search space of a UE. Athird sending module is configured to send only PDCCH signaling with aCIF to the UE in a physically overlapped region between the first searchspace and the second search space after receiving RRC ConnectionReconfiguration Complete signaling sent by the UE if the physicallyoverlapped region exists and a length of PDCCH signaling with no CIF inthe first search space is equal to a length of the PDCCH signaling withthe CIF in the second search space after the third determining moduledetermines the locations of the first search space and the second searchspace of the UE.

A UE according to an embodiment of the present invention includes areceiving module that is configured to receive PDCCH signaling with noCIF sent by a base station in a physically overlapped region between afirst search space and a second search space if the physicallyoverlapped region exists and a length of the PDCCH signaling with no CIFin the first search space is equal to a length of PDCCH signaling withthe CIF in the second search space. A parsing module is configured toparse the PDCCH signaling received by the receiving module according toonly a set rule of parsing PDCCH signaling with no CIF.

Another UE according to an embodiment of the present invention includesa second receiving module that is configured to receive PDCCH signalingwith a CIF in a physically overlapped region between a first searchspace and a second search space after the UE parses RRC Configurationsignaling from a base station correctly if the physically overlappedregion exists and a length of PDCCH signaling with no CIF in the firstsearch space of the UE is equal to a length of the PDCCH signaling withthe CIF in the second search space of the UE. A second parsing module isconfigured to parse the PDCCH signaling with the CIF received by thereceiving module according to only a set rule of parsing PDCCH signalingwith the CIF.

A communication system according to an embodiment of the presentinvention includes the foregoing base station and the UE, where the basestation includes the first determining module and the first sendingmodule, and the UE includes the receiving module and the parsing module.

Another communication system according to an embodiment of the presentinvention includes a UE and the foregoing base station which includesthe second determining module and the second sending module.

With the method, base station, UE, and system for sending and receivingPDCCH signaling according to the embodiments of the present invention,the scheduling uncertainty of the base station is prevented, and the UEcan determine whether the PDCCH signaling includes a CIF or not uponreceiving the PDCCH signaling, and can parse the signaling correctly.

BRIEF DESCRIPTION OF THE DRAWINGS

To make the technical solution of the present invention clearer, thefollowing describes the accompanying drawings involved in thedescription of the embodiments of the present invention. Apparently, theaccompanying drawings described below involve in some embodiment of thepresent invention, and persons skilled in the art can derive otherdrawings from such accompanying drawings without any creative effort.

FIG. 1 is a flowchart of a method for sending PDCCH signaling accordingto an embodiment of the present invention;

FIG. 2 is a flowchart of a method for sending PDCCH signaling accordingto another embodiment of the present invention;

FIG. 3 is a flowchart of a method for sending PDCCH signaling accordingto another embodiment of the present invention;

FIG. 4 is a flowchart of a method for sending PDCCH signaling accordingto another embodiment of the present invention;

FIG. 5 is a flowchart of a method for receiving PDCCH signalingaccording to an embodiment of the present invention;

FIG. 6 is a flowchart of a method for receiving PDCCH signalingaccording to another embodiment of the present invention;

FIG. 7 is a flowchart of a method for receiving PDCCH signalingaccording to another embodiment of the present invention;

FIG. 8 is a schematic structural diagram of a base station according toan embodiment of the present invention;

FIG. 9 is a schematic structural diagram of a base station according toanother embodiment of the present invention; and

FIG. 10 is a schematic structural diagram of a UE according to anembodiment of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

To make the objective, technical solution, and merits of the presentinvention clearer, the following describes the technical solution of thepresent invention in detail with reference to embodiments andaccompanying drawings. Evidently, the embodiments are exemplary onlypart of but not all of embodiments of the present invention. All otherembodiments, which can be derived by those skilled in the art from theembodiments provided herein without any creative effort, shall fallwithin the protection scope of the present invention.

In a communication system such as a Long Term Evolution (LTE) system, abase station, such as an eNB, schedules resources on one carrier with aUE. The minimum time unit for the base station to schedule resources isa subframe which is 1 millisecond in length. After the scheduled UEdemodulates and decodes PDCCH signaling in the search space of the PDCCHaccording to the length of the PDCCH signaling and the Control ChannelElement (CCE) level of the search space, and the scheduled UE uses aRadio Network Temporary Identifier (RNTI) of the scheduled UE to performdescrambling and Cyclic Redundancy Check (CRC) to check and determineswhether currently detected PDCCH signaling is PDCCH signaling of thescheduled UE. If the scheduled UE determines that the currently detectedPDCCH signaling is the PDCCH signaling of the UE, the UE furtherperforms follow-up operations. The PDCCH signaling carriestime-frequency resource allocation information indicative of a physicaldata channel (either an uplink physical data channel or a downlinkphysical data channel).

A search space is a set of logically consecutive CCEs. A CCE is aminimum unit that makes up PDCCH signaling. The PDCCH signaling of theUE may be transmitted by using four CCE levels: 1, 2, 4, and 8respectively. Different CCE levels have different encoding rates. ThePDCCH signaling at each different CCE level has a different searchspace, but physically, the different search spaces concerning the PDCCHsignaling may overlap each other. That is, different search spaces mayinclude CCEs, part of or all indices of which are the same.

Search spaces are classified into Common Search Space (CSS) andUE-specific Search Space (UESS). A CSS and a UESS are different searchspaces, but may physically overlap. That is, different search spaces mayinclude CCEs, part of or all indices of which are the same. The CSS is aspace all UEs need to detect. A CSS includes 16 CCEs, and in the CSSonly PDCCH signaling whose CCE level is 4 or 8 can be transmitted. Thenumber of searches in the CSS corresponding to CCE level 4 is 4, and thenumber of searches in the CSS corresponding to CCE level 8 is 2(4*4=8*2=16). Each UE has a specific UESS. Each UESS is decided by aspecific RNTI and a subframe number. The CCE level in a UESS is 1, 2, 4,or 8, and the number of searches in the UESS corresponding to CCE levels1, 2, 4, and 8 is 6, 6, 2, and 2 respectively.

The Downlink Control Information (DCI) format of the PDCCH signalingvaries with a transmission mode of scheduling data and a resourceallocation mode, and so on. For example, the DCI format may include DCIformat 0, DCI format 1A, DCI format 1B, DCI format 1C, DCI format 1D,DCI format 1, DCI format 2, DCI format 2A, DCI format 2, and DCI format3A. Generally, the length of PDCCH signaling in different formatsvaries, and the RNTI for scrambling the PDCCH signaling may also vary.In some scenarios, the PDCCH signaling in different DCI formats may havethe same length.

The PDCCH signaling for scheduling information shared by multiple UEsmay be placed in a CSS for transmission, and the RNTI used forscrambling the PDCCH signaling may also be an RNTI shared by multipleUEs. For example, the RNTI shared by multiple UEs may be a paging RNTI(paging RNTI), system information RNTI (system information RNTI), RandomAccess Channel Response RNTI (RACH Response RNTI), or Transmission PowerControl (TPC)-related RNTI.

The PDCCH signaling scrambled by using a UE-specific RNTI is generallyplaced in a UESS for transmission, for example, PDCCH signalingscrambled by using a Semi-Persistent Scheduling-Cell-RNTI (SPS-C-RNTI)or Cell-RNTI (C-RNTI).

The PDCCH signaling in DCI format 1A may be transmitted in the CSS, andthe PDCCH signaling is scrambled by using a paging RNTI, systeminformation RNTI, or RACH Response RNTI. The PDCCH signaling in DCIformat 1A may also be transmitted in the UESS, and the PDCCH signalingis scrambled by using a cell RNTI or an SPS-C-RNTI.

The length of the PDCCH signaling in DCI format 1A is the same as thelength of the PDCCH signaling in the following formats: DCI format 3,DCI format 3A, and DCI format 0. The PDCCH signaling in DCI format 1A isdifferentiated from the PDCCH signaling in DCI format 0 by using aheader discrimination bit. The PDCCH signaling in DCI format 1A and thePDCCH signaling in DCI format 0 are differentiated from the PDCCHsignaling in DCI format 3 and the PDCCH signaling in DCI format 3A byusing different RNTIs to scramble.

The PDCCH signaling in DCI format 1A scrambled by using the cell RNTIand the PDCCH signaling in DCI format 1A scrambled by using theSPS-C-RNTI, may be transmitted in the UESS or the CSS, which does notincrease the number of times that the PDCCH signaling is detected. Thenumber of times that the UE detects PDCCH signaling is related to thelength of the signaling. One more type of signaling length increases thenumber of times that detection is performed by one series. The PDCCHsignaling in DCI format 3 or the PDCCH signaling in DCI format 3Atransmitted in the CSS always needs to be detected, and the length ofsuch two types of PDCCH signaling is equal to the length of the PDCCHsignaling in DCI format 0 and the PDCCH signaling in DCI format 1A.Therefore, the number of times that the UE detects PDCCH signaling doesnot increase.

The base station configures one of seven transmission modes for the UEthrough a semi-static RRC signaling according to a data transmissionmode and a resource allocation mode. In each transmission mode, the UEneeds to detect the PDCCH signaling in at least two DCI formats. ThePDCCH signaling in one DCI format is related to the transmission modeallocated to the UE currently, and the PDCCH signaling in the other DCIformat is the PDCCH signaling in DCI format 1A and the PDCCH signalingin DCI format 0 that are unrelated to the transmission mode allocated tothe UE currently. That is, the UE needs to detect the PDCCH signaling inDCI format 1A and the PDCCH signaling in DCI format 0 regardless of thetransmission mode allocated to the UE. For example, if the base stationallocates transmission mode 3, that is, open-loop Multiple InputMultiple Output (MIMO) transmission mode, to the UE, the UE needs todetect the PDCCH signaling in DCI format 2A, and the UE also needs todetect the PDCCH signaling in DCI format 0 and the PDCCH signaling inDCI format 1A, where the PDCCH signaling in DCI format 2A is related totransmission mode 3. If the base station allocates transmission mode 4,that is, a closed-loop MIMO transmission mode, to the UE, the UE needsto detect the PDCCH signaling in DCI format 2, and the UE also needs todetect the PDCCH signaling in DCI format 0 and the PDCCH signaling inDCI format 1A, where PDCCH signaling in DCI format 2 is related totransmission mode 4.

Assuming scenario A: In the period from the base station sendingsemi-static RRC signaling that is used for notifying the UE of thecurrent resource scheduling mode to the base station receiving RRCConnection Reconfiguration Complete signaling returned by the UE, andafter the base station receives the RRC Connection ReconfigurationComplete signaling returned by the UE, it is possible that the length ofthe PDCCH signaling, in DCI format 0 with no CIF or DCI format 1A withno CIF, in the CSS of the current carrier is equal to the length ofPDCCH signaling with the CIF, in another format, in the UESS of thecurrent carrier, where the latter PDCCH signaling is used to scheduleanother carrier whose bandwidth is less than the bandwidth of thecurrent carrier. If a physically overlapped region between the CSS andthe UESS exists, the UE incorrectly parses the signaling and mistakenlydetermines that the PDCCH signaling detected in the physicallyoverlapped region is used to schedule the resources on the currentcarrier or schedule the resources on another carrier whose bandwidth isless than the bandwidth on the current carrier.

For example, one piece of signaling is PDCCH signaling in DCI format 0with no CIF or DCI format 1A with no CIF in the CSS of the currentcarrier CC1 and the other piece of signaling is PDCCH signaling with theCIF that is in another format in the UESS of CC1 and is used to schedulecarrier CC2 whose bandwidth is less than the bandwidth of CC1. Becausethe bandwidth of the carrier CC2 that is scheduled is less than thebandwidth of the carrier CC1, the number of resource allocation bitsrequired in the PDCCH signaling is smaller, and therefore it is possiblethat the length of the PDCCH signaling in DCI format 0 with no CIF orDCI format 1A with no CIF in the CSS of the current carrier CC1 is equalto the length of the PDCCH signaling with the CIF that is in anotherformat in the UESS of CC1 and is used to schedule carrier CC2 whosebandwidth is less than the bandwidth of CC1. When a physicallyoverlapped region between the CSS and the UESS exists, the UE may parsethe signaling incorrectly and mistakenly determine that the PDCCHsignaling detected in the physically overlapped region is used toschedule the resources in CC1 or schedule the resources in CC2.

Taking downlink data as an example, once the UE parses the PDCCHsignaling incorrectly, the UE will receive downlink data on a wrongcarrier. Subsequently, the UE may feedback a Negative Acknowledgement(NACK) message to the base station, and the base station may resend thedata. However, the UE is still unsure how to parse the PDCCH signalingcorrectly, and the UE is still unable to receive the data correctly. Thebuffer of the UE keeps storing the incorrect data until the base stationcompletes the maximum number of retransmissions, which leads to HybridAutomatic Repeat-reQuest (HARD) buffer pollution of the UE.

The following describes a solution to the foregoing problem in detail.In the embodiments of the present invention, for example, it is assumedthat in CCS data scheduling mode, the PDCCH signaling in DCI format 1Aor DCI format 0 transmitted in the CSS does not include a CIF, and thePDCCH signaling in DCI format 1A or DCI format 0 can be used to scheduleonly the resources on the current carrier of the PDCCH signaling or theresources on the uplink carrier corresponding to the carrier; or it isassumed that in CCS data scheduling mode, the PDCCH signalingtransmitted in a certain UESS does not include a CIF, and the PDCCHsignaling can be used to schedule only the resources on the currentcarrier of the PDCCH signaling or the resources on the uplink carriercorresponding to the carrier. Other scenarios may also be included.

FIG. 1 is a flowchart of a method for sending PDCCH signaling accordingto an embodiment of the present invention. The method includes thefollowing steps.

Step 101: The base station determines locations of a first search spaceand a second search space. The PDCCH signaling transmitted in the firstsearch space may include no CIF, and the first search space may be a CSSand/or UESS; the PDCCH signaling transmitted in the second search spacemay include a CIF, and the second search space may be a UESS.

The first search space may be at least one of a CSS and a UESS.

Step 102: The base station sends PDCCH signaling with no CIF to the UEin a physically overlapped region between the first search space and thesecond search space if the physically overlapped region exists and alength of the PDCCH signaling with no CIF in the first search space isequal to a length of the PDCCH signaling with the CIF in the secondsearch space.

The base station may determine that search spaces in which differentPDCCH signaling is may overlap, that is, part or all of CCEs with thesame indices are physically overlapped region, by determining thatdifferent search spaces include CCEs part or all of indices of which arethe same.

The method may further include determining the physically overlappedregion between the first search space and the second search spaceaccording to the locations of the first search space and the secondsearch space.

As an example, determining the physically overlapped region between thefirst search space and the second search space includes determining thatthe first search space and the second search space include at least oneCCE with the same index, where the at least one CCE with the same indexis the physically overlapped region.

The PDCCH signaling sent by the base station may include resourceallocation information and other control information such as carrieractivation or deactivation information, and information for triggering aphysical random access process.

As an example, in a physical region other than the foregoing physicallyoverlapped region in the search space of the user equipment, the basestation may send the PDCCH signaling according to the prior art, whichis not detailed here.

The embodiment shown in FIG. 1 restricts that in the physicallyoverlapped region between two search spaces the PDCCH signaling of oneof the search spaces is transmitted, which is essentially a search spaceorthogonalization method. Another search space orthogonalization methodmay be applied, which makes two search spaces not overlap and thereforesolves the problem of uncertainty of base station scheduling that iscaused by equal length, namely, the length of the PDCCH signaling withno CIF in the first search space is equal to the length of the PDCCHsignaling with the CIF in the second search space. For example, if a CSSoverlaps a UESS physically, the CSS location remains unchanged, and aconfiguration parameter is set to prevent overlap between the UESS andthe CSS without changing the CCE size of the CSS and the UESS,specifically, to make the UESS and the CSS place in tandem.

Because the base station uses the PDCCH signaling with no CIF forscheduling before and after RRC configuration, the scheduling mode ofthe PDCCH signaling before the RRC configuration is consistent with thescheduling mode after the RRC configuration, and therefore thescheduling uncertainty is prevented. Because the UE uses the PDCCHsignaling with no CIF for parsing before and after the RRCconfiguration, the parsing of the PDCCH signaling on the base station isconsistent with the parsing of the PDCCH signaling on the UE, andtherefore a parsing error is prevented. For example, when the UE failsto receive the RRC configuration signaling correctly, the UE stillparses the signaling according to a rule of parsing PDCCH signaling withno CIF, and if the base station has performed the scheduling using newlyconfigured PDCCH signaling with the CIF, the UE parses the signalingincorrectly. If the UE receives the RRC configuration signalingcorrectly but the base station still performs the scheduling using thePDCCH signaling with no CIF, the UE parses the signaling according to arule of parsing PDCCH signaling with the CIF, and therefore the parsingis incorrect.

Therefore, by sending only the PDCCH signaling with no CIF in thephysically overlapped region, the embodiment of the present inventionprevents uncertainty, and prevents the UE from parsing the signalingincorrectly.

FIG. 5 is a flowchart of a method for receiving PDCCH signalingaccording to an embodiment of the present invention. The method includesthe following steps.

Step 501: If a physically overlapped region between the first searchspace and the second search space exists and the length of the PDCCHsignaling with no CIF in the first search space is equal to the lengthof the PDCCH signaling with the CIF in the second search space, the UEreceives, in the physically overlapped region, the PDCCH signaling withno CIF sent by the base station.

Step 502: The UE parses the PDCCH signaling according to a set rule. Theset rule may specify that the base station and the UE parse the PDCCHsignaling according to a predetermined meaning of each field in thePDCCH signaling.

If the PDCCH signaling sent by the base station includes no CIF, the UEcan parse the PDCCH signaling according to a rule of parsing PDCCHsignaling with no CIF after the UE receives the PDCCH signaling. Thespecific rule of the parsing is negotiated by the UE and the basestation beforehand.

In the foregoing embodiment, in the case that a physically overlappedregion between the first search space and the second search space existsand the length of the PDCCH signaling with no CIF in the first searchspace is equal to the length of the PDCCH signaling with the CIF in thesecond search space, the base station is required to send the PDCCHsignaling with no CIF to the UE. In this way, only the PDCCH signalingwith no CIF is sent to the UE, and the UE is sure that the PDCCHsignaling received in the physically overlapped region includes no CIF,and the resources allocated in the PDCCH signaling are surely resourcesthat come from the carrier that is used to bear the PDCCH signaling,which prevents the UE from parsing the signaling incorrectly.

For example, in the period from the base station sending semi-static RRCsignaling that is used to notify the UE of the current resourcescheduling mode to the base station receiving RRC ConnectionReconfiguration Complete signaling returned by the UE, and after thebase station receives the RRC Connection Reconfiguration Completesignaling returned by the UE, if the length of PDCCH signaling with noCIF, in DCI format 0 or DCI format 1A, in the CSS of the current carrierin the UE that is used to bear PDCCH signaling, is equal to the lengthof PDCCH signaling with the CIF, in another format, in the UESS of theUE on the current carrier, where the PDCCH signaling with the CIF isused to schedule another carrier whose bandwidth is less than thebandwidth on the current carrier, and if a physically overlapped regionbetween the CSS and the UESS exists, the base station sends PDCCHsignaling with no CIF in the physically overlapped region, and the PDCCHsignaling carries the resource allocation information specific to theUE. In an embodiment, the UE and the base station may negotiatebeforehand that all PDCCH signaling sent in the physically overlappedregion includes no CIF. Therefore, after receiving the PDCCH signaling,the UE is sure that the PDCCH signaling includes no CIF, and theresources allocated in the PDCCH signaling surely resources that comefrom the carrier that is used to bear the PDCCH signaling, whichprevents the UE from parsing the signaling incorrectly.

In the embodiments shown in FIG. 1 and FIG. 5, the first search spacemay be a CSS, the second search space is a UESS, and the CCE level ofthe first search space and the second search space may be 4 or 8.Alternatively, the first search space and the second search spaceinclude two UESSs that are used to schedule different CCs of the UE.

As described above, The UE may determine that search spaces in whichdifferent PDCCH signaling is may overlap, that is, part or all of CCEswith the same indices are physically overlapped region, by determiningthat different search spaces include CCEs part or all of indices ofwhich are the same.

The foregoing method may further include determining locations of afirst search space and a second search space of a UE and determining thephysically overlapped region between the first search space and thesecond search space according to the locations of the first search spaceand the second search space.

As an example, determining the physically overlapped region between thefirst search space and the second search space includes determining thatthe first search space and the second search space comprise at least oneCCE with the same index, where the at least one CCE with the same indexis the physically overlapped region.

The UE knows that the length of the PDCCH signaling with no CIF in thefirst search space is equal to the length of the PDCCH signaling withthe CIF in the second search space. For example, as described above, thebase station configures one of seven transmission modes for the UEthrough semi-static RRC signaling according to the data transmissionmode and the resource allocation mode. The UE needs to detect the PDCCHsignaling in at least two DCI formats to obtain the length of the PDCCHsignaling.

In the embodiment shown in FIG. 1, if the first search space is a CSSand the second search space is a UESS, the restriction on the secondsearch space is not intense. That is because: in the second searchspace, even if the length of the PDCCH signaling at CCE level 4 or 8 isequal to the length of the PDCCH signaling with no CIF in the CSS, whichmakes the base station unable to transmit the PDCCH signaling in thephysically overlapped region, the base station can still transmit thePDCCH signaling at CCE level 1 or 2 in the physically overlapped region.Even if the length of the PDCCH signaling at CCE level 4 is equal to thelength of the PDCCH signaling with no CIF in the CSS, which makes thebase station unable to transmit the PDCCH signaling in the physicallyoverlapped region, the base station may still transmit the PDCCHsignaling at CCE level 8 so long as the PDCCH signaling at CCE level 8is transmitted in the second search space which does not overlap theCSS.

In the foregoing embodiment, in the period from the base station sendingthe RRC signaling to the base station receiving the RRC ConnectionReconfiguration Complete signaling returned by the UE, the base stationclearly knows the receiving mode of the UE, which solves the problemthat the UE incorrectly parses the control signaling that is transmittedby the base station.

In addition, the scheduling freedom of the first search space isreserved completely, namely, no scheduling restriction is imposed on thefirst search space, which overcomes the scheduling uncertainty of thebase station during the RRC reconfiguration period to the greatestextent.

FIG. 2 is a flowchart of a method for sending PDCCH signaling accordingto another embodiment of the present invention. The method includes thefollowing steps.

Step 201: A base station determines locations of a first search spaceand a second search space.

Step 202: The base station sends third PDCCH signaling or fourth PDCCHsignaling to the UE in a physically overlapped region between the firstsearch space and the second search space within a time interval fromsending Radio Resource Control (RRC) signaling to the UE to receivingRRC Connection Reconfiguration Complete signaling returned by the UE,wherein the third PDCCH signaling is PDCCH signaling with no CarrierIndication Field (CIF) and the fourth PDCCH signaling is PDCCH signalingwith the CIF if a length of first PDCCH signaling in the first searchspace is equal to a length of second PDCCH signaling in the secondsearch space and the physically overlapped region exists, wherein thefirst PDCCH signaling is PDCCH signaling with no CIF, and the secondPDCCH signaling is PDCCH signaling with the CIF, and a length of thethird PDCCH signaling is unequal to a length of the fourth PDCCHsignaling, and the length of the third PDCCH signaling is different fromthe length of the first PDCCH signaling, and the length of the fourthPDCCH signaling is different from the length of the first PDCCHsignaling.

After receiving the RRC Connection Reconfiguration Complete signalingreturned by the UE, the base station sends the second PDCCH signaling,namely, the PDCCH signaling with the CIF to the UE. The third PDCCHsignaling or the fourth PDCCH signaling may be other types of PDCCHsignaling than the first PDCCH signaling and the second PDCCH signaling.The other types of PDCCH signaling than the first PDCCH signaling andthe second PDCCH signaling is PDCCH signaling which is not parsed by theUE incorrectly. For example, it is assumed that PDCCH signaling in twoformats exists currently under each transmission mode; in two types ofPDCCH signaling (with the CIF) under a certain transmission modecorresponding to a carrier scheduled across carriers, assuming that thelength of one type of PDCCH signaling is equal to the length of thePDCCH signaling with no CIF and in a certain format in the CSS of acarrier of the PDCCH, the eNB may send the other type of PDCCH signalingunder the current mode, and the length of the other type of PDCCHsignaling is unequal to the length of the PDCCH signaling with no CIF ina certain format in the CSS of a carrier of the PDCCH. In this case, theUE may not parse the PDCCH signaling incorrectly.

Alternatively, two types of UE-specific PDCCH signaling with no CIF mayexist in the CSS of the carrier of the PDCCH, and one type may be parsedby the UE incorrectly. If one type is parsed by the UE incorrectly, thebase station may send the other type of PDCCH signaling with no CIF tothe UE.

FIG. 6 is a flowchart of a method for receiving PDCCH signalingaccording to another embodiment of the present invention. The methodincludes the following steps.

Step 601: If the length of the PDCCH signaling with no CIF in a firstsearch space is equal to the length of the PDCCH signaling with the CIFin a second search space, and a physically overlapped region existsbetween the first search space and the second search space, a UEreceives, in the physically overlapped region, PDCCH signaling with theCIF sent by a base station after the UE parses RRC signaling correctly.

Step 602: The UE parses the PDCCH signaling with the CIF according toonly a set rule of parsing PDCCH signaling with the CIF.

If the PDCCH signaling sent by the base station includes the CIF, the UEmay parse the PDCCH signaling according to a rule of parsing PDCCHsignaling with the CIF after the UE receives the PDCCH signaling. Thespecific rule of parsing which the UE uses is negotiated by the UE andthe base station beforehand.

In the foregoing embodiment, in a case that the length of the PDCCHsignaling with no CIF in the first search space is equal to the lengthof the PDCCH signaling with the CIF in the second search space and aphysically overlapped region exists between the first search space andthe second search space, the base station cannot send the PDCCHsignaling with the CIF within a time interval from the base stationsending the RRC signaling to the base station receiving the RRCConnection Reconfiguration Complete signaling returned by the UE. The UEmay not receive RRC configuration signaling correctly and thereforeregard that the received PDCCH signaling includes no CIF, which leads toa parsing error. Therefore, after receiving the RRC ConnectionReconfiguration Complete signaling returned by the UE, the base stationmay send the PDCCH signaling with the CIF to the UE.

However, within a time interval from the base station sending RRCsignaling to the base station receiving the RRC ConnectionReconfiguration Complete signaling returned by the UE, the base stationmay send only other types of PDCCH signaling than the first PDCCHsignaling and the second PDCCH signaling to the UE. For the UE side,after parsing the RRC configuration signaling correctly, the UE receivesonly the PDCCH signaling with the CIF sent by the base station.

In the embodiment shown in FIG. 2, the first search space may be a CSS,the second search space is a UESS, and the CCE level of the first searchspace and the second search space is 4 or 8. Alternatively, the firstsearch space and the second search space include two UESSs that are usedto schedule a different CC of the UE.

If the first search space is a CSS and the second search space is aUESS, the method shown in FIG. 2 is applicable, which does not increasethe number of times that PDCCH signaling is checked in the first searchspace. In addition, the scheduling freedom of the second search space isgreater than that of the first search space (because the second searchspace can implement cross-carrier scheduling, but the first search spaceallows only same-carrier scheduling). Therefore, this solution reservesthe scheduling freedom of the second search space completely, and doesnot impose any scheduling restriction on the second search space.

FIG. 3 is a flowchart of a method for sending PDCCH signaling accordingto another embodiment of the present invention. The method includes thefollowing steps.

Step 301: A base station determines locations of a first search spaceand a second search space.

Step 302: If a length of the first PDCCH signaling with no CIF in thefirst search space is equal to a length of the second PDCCH signalingwith the CIF in the second search space and a physically overlappedregion between the first search space and the second search spaceexists, the base station sends, in the physically overlapped region,other types of PDCCH signaling than the first PDCCH signaling and thesecond PDCCH signaling to the UE within a time interval from the basestation sending RRC signaling to the UE to the base station receivingRRC Connection Reconfiguration Complete signaling returned by the UE.

The other types of PDCCH signaling than the first PDCCH signaling andthe second PDCCH signaling may be third PDCCH signaling with no CIF orfourth PDCCH signaling with the CIF. The length of the third PDCCHsignaling with no CIF is unequal to the length of the fourth PDCCHsignaling with the CIF.

The embodiment shown in FIG. 3 can solve the problem that exists inscenario B below.

Assuming scenario B: PDCCH signaling for scheduling two carriers has arespective and independent UESS on one carrier, and a physicallyoverlapped region between the two UESSs exists. In this case, theproblem of uncertainty of the scheduling within the period from the basestation sending semi-static RRC signaling that is used to notify the UEof the current resource scheduling mode to the base station receivingRRC Connection Reconfiguration Complete signaling returned by the UE.For example, before the sending, the resource scheduling mode of the UEis SCS, and the PDCCH signaling transmitted by the base station to theUE includes no CIF. After the UE receives the semi-static RRC signalingthat is used to notify the UE of the current resource scheduling mode,the resource scheduling mode of the UE changes to CCS.

When the base station does not receive the RRC ConnectionReconfiguration Complete signaling returned by the UE, the base stationis not sure whether the PDCCH signaling sent to the UE needs to includethe CIF, which leads to scheduling uncertainty of the base station.After the UE receives the RRC configuration signaling from the basestation correctly and changes the resource scheduling mode to CCS, theCIF may be added to the PDCCH signaling in the two UESSs above, thePDCCH signaling for scheduling different carriers is distinguishedautomatically, and the foregoing problem may not occur even if thelength of one piece of PDCCH signaling with the CIF is equal to thelength of another piece of PDCCH signaling with the CIF.

In scenario B, the problem still exists if the base station sends onlythe PDCCH signaling with the CIF or the PDCCH signaling with no CIFwithin a time interval from sending semi-static RRC signaling toreceiving RRC Connection Reconfiguration Complete signaling returned bythe UE. If the base station sends only the PDCCH signaling with no CIFwithin a time interval from the base station sending the semi-static RRCsignaling to the base station receiving the RRC ConnectionReconfiguration Complete signaling returned by the UE, but the UE hasparsed the semi-static RRC signaling correctly, the UE regards that thereceived PDCCH signaling includes the CIF, which leads to a parsingerror.

If the base station sends only the PDCCH signaling with the CIF within atime interval from the base station sending the semi-static RRCsignaling to the base station receiving the RRC ConnectionReconfiguration Complete signaling returned by the UE, but the UE hasnot parsed the semi-static RRC signaling correctly, the UE regards thatthe received PDCCH signaling includes no CIF, which leads to a parsingerror.

If the embodiment shown in FIG. 3 is applied, namely, the base stationsends other types of PDCCH signaling than the first PDCCH signaling andthe second PDCCH signaling in the physically overlapped region, thescheduling uncertainty of the base station is prevented, and the parsingerror on the UE is prevented.

After the base station receives the RRC Connection ReconfigurationComplete signaling returned by the UE, the resource scheduling mode ofthe UE changes to CCS. Even if a physically overlapped region betweenthe two UESSs of the UE exists, the base station may not be uncertain ofscheduling and the UE may not parse the signaling incorrectly becauseany PDCCH signaling under the CCS mode includes the CIF.

In the embodiment shown in FIG. 3, the first search space and the secondsearch space include two UESSs that are used to schedule different CCsof the UE.

With the method shown in FIG. 3, the base station prevents the UE fromparsing the signaling incorrectly, without specifying any activity ofthe UE, namely, without affecting operations of the UE. The method issimple, and operations are easy.

In an embodiment, a UE has two CCs: CC1 and CC2, PDCCH signaling istransmitted over CC1, and CC1 includes search space CSS, search spaceUESS1, and search space UESS2; the PDCCH signaling in the CSS on CC1 isused to schedule CC1 and the PDCCH signaling includes no CIF; the PDCCHsignaling in UESS1 on CC1 is used to schedule CC1 and the PDCCHsignaling includes no CIF; the PDCCH signaling in UESS2 on CC1 is usedto schedule CC2 across carriers and the PDCCH signaling includes theCIF.

In a scenario, if the length of the PDCCH signaling with no CIF in UESS1is equal to the length of the PDCCH signaling with the CIF in UESS2, anda physically overlapped region between UESS1 and UESS2 exists, the basestation sends, in the physically overlapped region, the PDCCH signalingwith no CIF to the UE; and, if the length of the PDCCH signaling with noCIF in the CSS is equal to the length of the PDCCH signaling with theCIF in UESS2, and a physically overlapped region between the CSS andUESS2 exists, the base station sends, in the physically overlappedregion, the PDCCH signaling with the CIF to the UE; therefore, if thelength of the PDCCH signaling with no CIF in UESS1 is equal to thelength of the PDCCH signaling with the CIF in UESS2, and is also equalto the length of the PDCCH signaling with the CIF in the CSS, and aphysically overlapped region between UESS1, UESS2, and the CSS exists,the problem of uncertainty of the scheduling exists in the physicallyoverlapped region between UESS1, UESS2, and the CSS.

Or, if the length of the PDCCH signaling with no CIF in UESS1 is equalto the length of the PDCCH signaling with the CIF in UESS2, and aphysically overlapped region between UESS1 and UESS2 exists, the basestation sends the PDCCH signaling with the CIF to the UE in thephysically overlapped region; and, if the length of the PDCCH signalingwith no CIF in the CSS is equal to the length of the PDCCH signalingwith the CIF in UESS2, and a physically overlapped region between theCSS and UESS2 exists, the base station sends the PDCCH signaling withthe CIF to the UE in the physically overlapped region; therefore, if thelength of the PDCCH signaling with no CIF in UESS1 is equal to thelength of the PDCCH signaling with the CIF in UESS2, and is also equalto the length of the PDCCH signaling with no CIF in the CSS, and aphysically overlapped region between UESS1, UESS2, and the CSS exists,the problem of uncertainty of the scheduling exists in the physicallyoverlapped region between UESS1, UESS2, and the CSS.

Based on the preceding case, in an embodiment of the present invention,the base station sends only the PDCCH signaling with no CIF to the UE orsends only the PDCCH signaling with the CIF to the UE in the physicallyoverlapped region between UESS1, UESS2, and the CSS.

If the base station sends only the PDCCH signaling with no CIF to the UEin the physically overlapped region between UESS1, UESS2, and the CSS,the data is placed onto CC1 of the PDCCH first, which ensures thescheduling priority of CC1 and ensures smooth transition of thescheduling during the RRC reconfiguration.

If the base station sends only the PDCCH signaling with the CIF to theUE in the physically overlapped region between UESS1, UESS2, and theCSS, the base station ensures the scheduling freedom of the UESS of CC2scheduled across carriers.

A method for sending PDCCH signaling according to an embodiment of thepresent invention includes determining locations of a first searchspace, a second search space, and a third search space of a UE andsending only PDCCH signaling with the CIF or only PDCCH signaling withthe CIF to the UE in a physically overlapped region between the firstsearch space, the second search space, and the third search space if thephysically overlapped region exists and length of the PDCCH signalingwith no CIF in the first search space is equal to length of the PDCCHsignaling with no CIF in the third search space and is equal to lengthof the PDCCH signaling with the CIF in the second search space.

A method for receiving PDCCH signaling according to an embodiment of thepresent invention includes the following steps.

A UE receives PDCCH signaling with the CIF or PDCCH signaling with noCIF sent by a base station in a physically overlapped region between afirst search space, a second search space, and a third search space ifthe physically overlapped region exists and length of the PDCCHsignaling with no CIF in the first search space is equal to length ofthe PDCCH signaling with no CIF in the third search space and is equalto length of the PDCCH signaling with the CIF in the second searchspace.

The UE parses the PDCCH signaling according to a set rule.

A base station includes a sixth determining module, configured todetermine locations of a first search space, a second search space, anda third search space of a UE and a sixth sending module, configured tosend only PDCCH signaling with the CIF or only PDCCH signaling with noCIF to the UE in a physically overlapped region between the first searchspace, the second search space, and the third search space if thephysically overlapped region exists and length of the PDCCH signalingwith no CIF in the first search space is equal to length of the PDCCHsignaling with no CIF in the third search space and is equal to lengthof the PDCCH signaling with the CIF in the second search space.

A UE includes a seventh receiving module, configured to receive PDCCHsignaling with the CIF or PDCCH signaling with no CIF sent by a basestation in a physically overlapped region between a first search space,a second search space, and a third search space if the physicallyoverlapped region exists and length of the PDCCH signaling with no CIFin the first search space is equal to length of the PDCCH signaling withno CIF in the third search space and is equal to length of the PDCCHsignaling with the CIF in the second search space. The UE also includesa seventh parsing module, configured to parse the PDCCH signalingaccording to a set rule.

FIG. 4 is a flowchart of a method for sending PDCCH signaling accordingto another embodiment of the present invention. The method includes thefollowing steps.

Step 401: A base station determines locations of a first search spaceand a second search space.

Step 402: The base station sends the PDCCH signaling with the CIF to aUE after adding a bit to the PDCCH signaling in a physically overlappedregion between the first search space and the second search space if thephysically overlapped region exists and the length of the PDCCHsignaling with no CIF in the first search space is equal to the lengthof the PDCCH signaling with the CIF in the second search space.

In this embodiment, the base station needs to add a bit to PDCCHsignaling that is with the CIF and send the PDCCH signaling to the UE ifa physically overlapped region between the first search space and thesecond search space exists and the length of the PDCCH signaling with noCIF in the first search space is equal to the length of the PDCCHsignaling with the CIF in the second search space. Because the receivedPDCCH signaling with the CIF is longer than the PDCCH signaling with noCIF by one bit, the UE knows that the longer PDCCH signaling includesthe CIF, and can parse the signaling correctly.

For example, in the period from the base station sending semi-static RRCsignaling that is used to notify the UE of the current resourcescheduling mode to the base station receiving RRC ConnectionReconfiguration Complete signaling returned by the UE, and after thebase station receives the RRC Connection Reconfiguration Completesignaling returned by the UE, if the length of PDCCH signaling, in DCIformat 0 or DCI format 1A, with no CIF, and in the CSS of the currentcarrier of the UE, is equal to the length of PDCCH signaling that iswith the CIF, in another format, and in the UESS of the current carrierof the UE, where the latter PDCCH signaling is used to schedule anothercarrier whose bandwidth is less than the bandwidth of the currentcarrier, and if a physically overlapped region between the CSS and theUESS exists (specific to CCE level 4 and CCE level 8), the base stationsends the PDCCH signaling with the CIF to a UE after adding a bit to thePDCCH signaling in the physically overlapped region. In this way, the UEknows that the received PDCCH signaling includes the CIF, preventing aparsing error of the UE.

Assuming that the first search space is a CSS and the second searchspace is a UESS, in the method shown in FIG. 4, the bit is added onlywhen the length of the PDCCH signaling with no CIF in the CSS is equalto the length of the PDCCH signaling with the CIF in the UESS. Aphysically overlapped region between the CSS and the UESS exists, and isspecific to CCE level 4 or CCE level 8, which generates few overheadsand does not affect the length of the PDCCH signaling with no CIF in theCSS. It is ensured that the PDCCH signaling with no CIF in the CSS iscompatible with the format of the PDCCH signaling in the LTE system.

The search spaces may physically overlap each other on different CCElevels, and different CCE levels correspond to different rates ofchannel codes. Therefore, when the length of the PDCCH signaling with anadded bit is equal to particular length, all the PDCCH signaling ondifferent CCE levels passes through the C-RNTI check of the UE, namely,all such signaling is parsed by the UE as the PDCCH signaling of the UE.However, the PDCCH signaling sent by the base station has only one ofthe CCE levels. Therefore, the UE parses the PDCCH signalingincorrectly. Therefore, in this embodiment, if the length of PDCCHsignaling with an added bit is equal to the length which causes thePDCCH signaling on different CCE levels to pass through the C-RNTI checkof the UE, one more bit needs to be added to prevent the PDCCH signalingon different CCE levels from passing through the C-RNTI check of the UE.

FIG. 7 is a flowchart of a method for receiving PDCCH signalingaccording to another embodiment of the present invention. The methodincludes the following steps.

Step 701: if the length of the PDCCH signaling with no CIF in a firstsearch space is equal to the length of the PDCCH signaling with the CIFin a second search space and a physically overlapped region between thefirst search space and the second search space exists, a UE receives, inthe physically overlapped region, PDCCH signaling that includes a CIF,sent by a base station, and added by one bit.

Step 702: The UE parses the PDCCH signaling according to a set rule.

If the PDCCH signaling sent by the base station includes an added bitand the CIF, the UE can parse the received signaling according to a ruleof parsing PDCCH signaling with the CIF and the added bit. The specificrule of parsing is negotiated by the UE and the base station beforehand.

In an embodiment, the base station may determine the locations of afirst search space and a second search space, and if the length of thePDCCH signaling with no CIF in the first search space is equal to thelength of the PDCCH signaling with the CIF in the second search space,and a physically overlapped region between the first search space andthe second search space exists, the base station may send only the PDCCHsignaling with the CIF to the UE in the physically overlapped regionafter receiving RRC Connection Reconfiguration Complete signaling sentby the UE.

The first search space is a CSS, and the second search space is a UESS.

In an embodiment, if the length of the PDCCH signaling with no CIF inthe first search space is equal to the length of the PDCCH signalingwith the CIF in the second search space, and a physically overlappedregion between the first search space and the second search spaceexists, where the PDCCH signaling with no CIF in the first search spaceis a first signaling and the PDCCH signaling with the CIF in the secondsearch space is a second signaling, and in the physically overlappedregion the first signaling may be distinguished from the secondsignaling by an existing bit, or a redundant bit, or a newly added bitor state whose absolute position is fixed in the PDCCH of the firstsignaling and the second signaling. “Absolute position is fixed” meansthat this field has a determined position in the PDCCH, for example, thelast bit except the CRC bit.

For example, in a Frequency Division Duplex (FDD) system, the uplinkcarrier bandwidth is equal to the downlink carrier bandwidth, and theDCI formats are DCI format 0 and DCI format 1A. In DCI format 1A, thelast bit except the CRC bit is a bit of a power command field; in DCIformat 0, the last bit except the CRC bit is a padding bit which is 0 bydefault. It may be specified that the last bit being “0” means the PDCCHsignaling is the first signaling, and that the last bit being “1” meansthe PDCCH signaling is the second signaling. If the last bit indicates ameaning, namely, if the last bit is not a redundant bit or a padding bitor state, the parsing of this field may be restricted, or another fieldin the PDCCH signaling can be used to express the meaning of this bit,for example, the meaning may be exchanged with the meaning of the powercontrol field in the PDCCH signaling intended for scheduling downlinkdata.

In an embodiment, in a system that supports CA, uplink control signaling(including uplink ACK/NACK, and uplink channel state information) is allfed back on an uplink carrier specific to the UE. The uplink carrier iscalled an uplink primary carrier, the downlink carrier paired with theuplink carrier is called a downlink primary carrier, and other downlinkcarriers of the UE are called downlink non-primary carriers. One of themethods for power control for an uplink control channel is to performcontrol through a 2-bit power control command field in the PDCCHsignaling intended for scheduling downlink data.

The data on uplink control channels corresponding to all downlinkcarriers of a UE is fed back on the uplink primary carrier only.Therefore, only the power control command field in the PDCCH signalingfor scheduling the downlink primary carrier needs to be used forperforming power control for uplink control channels, and the powercontrol command field in the PDCCH signaling for scheduling downlinknon-primary carriers is redundant for the power control. This redundantfield may be used to represent the inherent meaning of the foregoingfield which distinguishes the first signaling from the second signalingand has a fixed absolute position. The UE may use this field with afixed absolute position to distinguish the first signaling from thesecond signaling, and parse this redundant field to obtain the meaningexpressed by this field.

FIG. 8 is a schematic structural diagram of a base station according toan embodiment of the present invention. The base station 1 includes afirst determining module 11 and a first sending module 12. The firstdetermining module 11 is configured to determine locations of a firstsearch space and a second search space. The first sending module 12 isconfigured to send only PDCCH signaling with no CIF to the UE in aphysically overlapped region between the first search space and thesecond search space if the physically overlapped region exists and thelength of the PDCCH signaling with no CIF in the first search space isequal to the length of the PDCCH signaling with the CIF in the secondsearch space; or send PDCCH signaling that includes the CIF and is addedby one bit to the UE if the first PDCCH signaling is PDCCH signalingwith no CIF in the first search space, and the second PDCCH signaling isPDCCH signaling with the CIF in the second search space; or send anothertype of PDCCH signaling except the first PDCCH signaling and the secondPDCCH signaling to the UE within a time interval from the base stationsending RRC signaling to the UE to the base station receiving RRCConnection Reconfiguration Complete signaling returned by the UE; andsend only the PDCCH signaling with the CIF to the UE after the basestation receives the RRC Connection Reconfiguration Complete signalingreturned by the UE.

In an embodiment, a base station may include a third determining modulethat is configured to determine locations of a first search space and asecond search space of a UE. The base station may also include a thirdsending module that is configured to send only PDCCH signaling with theCIF to the UE in a physically overlapped region between the first searchspace and the second search space after receiving RRC ConnectionReconfiguration Complete signaling sent by the UE if the physicallyoverlapped region exists and a length of the PDCCH signaling with no CIFin the first search space is equal to a length of the PDCCH signalingwith the CIF in the second search space after the third determiningmodule determines the locations of the first search space and the secondsearch space of the UE.

The first search space is a CSS, and the second search space is a UESS.

FIG. 9 is a schematic structural diagram of a base station according toanother embodiment of the present invention. The base station 1includes: a second determining module 13 and a second sending module 14.The second determining module 13 is configured to determine locations ofa first search space and a second search space. The second sendingmodule 14 is configured to send third PDCCH signaling or fourth PDCCHsignaling to the UE in a physically overlapped region within a timeinterval from sending RRC signaling to the UE to receiving RRCConnection Reconfiguration Complete signaling returned by the UE, wherethe third PDCCH signaling is PDCCH signaling with no CIF and the fourthPDCCH signaling is PDCCH signaling with the CIF after the seconddetermining module determines the locations of the first search spaceand the second search space of the UE if a length of first PDCCHsignaling in the first search space is equal to a length of second PDCCHsignaling in the second search space where the first PDCCH signaling isPDCCH signaling with no CIF and the second PDCCH signaling is PDCCHsignaling with the CIF, and the physically overlapped region existsbetween the first search space and the second search space, where alength of the third PDCCH signaling is unequal to a length of the fourthPDCCH signaling, and the length of the third PDCCH signaling isdifferent from the length of the first PDCCH signaling and the length ofthe fourth PDCCH signaling is different from the length of the firstPDCCH signaling.

In the embodiment shown in FIG. 9, the first search space and the secondsearch space include two UESSs that are used to schedule different CCsof the UE.

FIG. 10 is a schematic structural diagram of a UE according to anembodiment of the present invention. The UE2 includes a receiving module21 and a parsing module 22. The receiving module 21 is configured toreceive PDCCH signaling with no CIF or receive PDCCH signaling sent by abase station that includes the CIF, added by one bit, in a physicallyoverlapped region between a first search space and a second search spaceif the physically overlapped region exists and a length of the PDCCHsignaling with no CIF in the first search space is equal to a length ofthe PDCCH signaling with the CIF in the second search space. The parsingmodule 22 is configured to parse the PDCCH signaling received by thereceiving module 21 according to only a set rule of parsing PDCCHsignaling with no CIF, or receive only the PDCCH signaling with the CIFsent by the base station after the UE parses RRC signaling correctly.

In an embodiment, the UE may further include a second receiving modulethat is configured to receive PDCCH signaling with the CIF in aphysically overlapped region between the first search space and thesecond search space after the UE parses RRC signaling from a basestation correctly if the physically overlapped region exists and alength of the PDCCH signaling with no CIF in the first search space ofthe UE is equal to a length of the PDCCH signaling with the CIF in thesecond search space of the UE. The UE may also include a second parsingmodule, configured to parse the PDCCH signaling with the CIF received bythe receiving module according to only a set rule of parsing PDCCHsignaling with the CIF.

A communication system is provided in an embodiment of the presentinvention. The communication system may include the base station shownin FIG. 8 and the UE shown in FIG. 10; the base station sends PDCCHsignaling to the UE by using the method described in the methodembodiment above, and the UE receives the PDCCH signaling from the basestation by using the method described in the method embodiment above.

Another communication system is provided in an embodiment of the presentinvention. The communication system may include a base station and theUE shown in FIG. 9; the base station sends PDCCH signaling to the UE byusing the method described in the method embodiment above, and the UEreceives the PDCCH signaling from the base station according to theprior art.

With the base station and the UE provided herein, the base station islimited that the base station sends the PDCCH signaling with no CIF tothe UE in the physically overlapped region between the first searchspace and the second search space if the physically overlapped regionexists and a length of the PDCCH signaling with no CIF in the firstsearch space is equal to a length of the PDCCH signaling with the CIF inthe second search space.

Alternatively, the base station sends another type of PDCCH signalingexcept the first PDCCH signaling and the second PDCCH signaling to theUE within a time interval from sending RRC signaling to the UE toreceiving RRC Connection Reconfiguration Complete signaling returned bythe UE; and the base station sends PDCCH signaling with the CIF to theUE after receiving the RRC Connection Reconfiguration Complete signalingreturned by the UE.

Alternatively, the base station sends another type of PDCCH signalingexcept the first PDCCH signaling and the second PDCCH signaling to theUE in the physically overlapped region between the first search spaceand the second search space within a time interval from sendingsemi-static RRC signaling to receiving RRC Connection ReconfigurationComplete signaling returned by the UE if the physically overlappedregion exists and a length of the first PDCCH signaling with no CIF inthe first search space is equal to a length of the second PDCCHsignaling with the CIF in the second search space. In this way, thescheduling uncertainty of the base station is prevented, and the parsingerror of the UE is prevented.

In an embodiment, the base station determines locations of a firstsearch space and a second search space; and the base station sends thePDCCH signaling with the CIF to the UE in a physically overlapped regionbetween the first search space and the second search space if thephysically overlapped region exists and a length of the PDCCH signalingwith no CIF in the first search space is equal to a length of the PDCCHsignaling with the CIF in the second search space.

The UE receives the PDCCH signaling with the CIF sent by the basestation in a physically overlapped region between the first search spaceand the second search space if the physically overlapped region existsand a length of the PDCCH signaling with no CIF in the first searchspace is equal to a length of the PDCCH signaling with the CIF in thesecond search space, and parses the PDCCH signaling according to a setrule.

If the PDCCH signaling sent by the base station includes the CIF, the UEcan parse the PDCCH signaling according to a rule of parsing PDCCHsignaling with the CIF after receiving the signaling. The specific ruleof parsing is negotiated by the UE and the base station beforehand.

In the foregoing embodiment, the base station needs to send PDCCHsignaling with the CIF to the UE if a physically overlapped regionexists between the first search space and the second search space and alength of the PDCCH signaling with no CIF in the first search space isequal to a length of the PDCCH signaling with the CIF in the secondsearch space. In this way, only the PDCCH signaling with the CIF is sentto the UE, and the UE is sure that the PDCCH signaling received in thephysically overlapped region includes the CIF, and the resourcesallocated in the PDCCH signaling are surely resources that come from thecarrier that is used to bear the PDCCH signaling, which prevents the UEfrom parsing the signaling incorrectly.

For example, in the period from the base station sending semi-static RRCsignaling that is used to notify the UE of the current resourcescheduling mode to the base station receiving RRC ConnectionReconfiguration Complete signaling returned by the UE, and after thebase station receives the RRC Connection Reconfiguration Completesignaling returned by the UE, if the length of PDCCH signaling with noCIF, in DCI format 0 or DCI format 1A, in the CSS of the current carrierin the UE that is used to bear PDCCH signaling, is equal to the lengthof PDCCH signaling with the CIF, in another format, in the UESS of theUE on the current carrier, where the PDCCH signaling with the CIF isused to schedule another carrier whose bandwidth is less than thebandwidth on the current carrier, and if a physically overlapped regionbetween the CSS and the UESS exists, the base station sends PDCCHsignaling with no CIF in the physically overlapped region, and the PDCCHsignaling carries the resource allocation information specific to theUE. In an embodiment, the UE and the base station may negotiatebeforehand that all PDCCH signaling sent in the physically overlappedregion includes no CIF. Therefore, after receiving the PDCCH signaling,the UE is sure that the PDCCH signaling includes no CIF, and theresources allocated in the PDCCH signaling surely resources that comefrom the carrier that is used to bear the PDCCH signaling, whichprevents the UE from parsing the signaling incorrectly.

The first search space may be a CSS, the second search space is a UESS,and the CCE level of the first search space and the second search spaceis 4 or 8. Alternatively, the first search space and the second searchspace include two UESSs that are used to schedule different CCs of theUE.

If the first search space is a CSS and the second search space is aUESS, the method shown in FIG. 2 is applicable, which does not increasethe number of times PDCCH signaling is checked in the first searchspace. In addition, the scheduling freedom of the second search space isgreater than that of the first search space (because the second searchspace can implement cross-carrier scheduling, but the first search spaceallows only same-carrier scheduling). Therefore, this solution reservesthe scheduling freedom of the second search space completely, and doesnot impose any scheduling restriction on the second search space.

A base station provided in an embodiment of the present inventionincludes a fourth determining module that is configured to determinelocations of a first search space and a second search space of a UE anda fourth sending module that is configured to send PDCCH signaling withthe CIF or PDCCH signaling with no CIF to the UE in a physicallyoverlapped region between the first search space and the second searchspace if the physically overlapped region exists and a length of thePDCCH signaling with no CIF in the first search space is equal to alength of the PDCCH signaling with the CIF in the second search spaceafter the first determining module determines the locations of the firstsearch space and the second search space of the UE.

A UE provided in an embodiment of the present invention includes afourth receiving module that is configured to receive PDCCH signalingwith the CIF or PDCCH signaling with no CIF sent by a base station in aphysically overlapped region between a first search space and a secondsearch space if the physically overlapped region exists and a length ofthe PDCCH signaling with no CIF in the first search space is equal to alength of the PDCCH signaling with the CIF in the second search space.The UE may also include a fourth parsing module, configured to parse thePDCCH signaling received by the receiving module according to a setrule.

Persons skilled in the art should understand that part of the steps ofthe method in the embodiments of the present invention may beimplemented by a program instructing relevant hardware. The program maybe stored in computer readable storage media. When the program runs, theprogram executes the steps of the method in the embodiments of thepresent invention. The storage media may be any media capable of storingprogram codes, such as a Read Only Memory (ROM), a Random Access Memory(RAM), a magnetic disk, or a Compact Disk-Read Only Memory (CD-ROM).

Finally, it should be noted that the above embodiments are merelyprovided for describing the technical solution of the present invention,but not intended to limit the present invention. It is apparent thatpersons skilled in the art can make various modifications, variations,and replacements to the invention without departing from the spirit andscope of the invention. The present invention is intended to cover themodifications, variations, and replacements provided that they fallwithin the scope of protection defined by the following claims or theirequivalents.

What is claimed is:
 1. A machine-readable storage medium having storedthereon, programming for execution by a machine, the programmingincluding instructions to: determine locations of a first search spaceand a second search space, wherein the first search space and the secondsearch space comprises a plurality of control channel elements (CCEs),and wherein the PDCCH signaling is made up of at least one CCE of thefirst search space or of the second search space; determine whether thefirst search space and the second search space overlap in at least oneof the plurality of CCEs, and determine whether a length of the PDCCHsignaling excluding a carrier indication field (CIF) in the first searchspace is equal to a length of the PDCCH signaling including the CIF inthe second search space; and when the first search space and the secondsearch space overlap in the at least one of the plurality of CCEs andwhen the length of the PDCCH signaling excluding the CIF in the firstsearch space is equal to the length of the PDCCH signaling including theCIF in the second search space, transmit, in the at least one of theplurality of CCEs over which the first search space and overlaps thesecond search space, the PDCCH signaling including the CIF to the UE. 2.The machine-readable storage medium according to claim 1, wherein thefirst search space is a common search space (CSS), and the second searchspace is a UE-specific search space (UESS).
 3. The machine-readablestorage medium according to claim 2, wherein a CCE level of the PDCCHsignaling in the CSS is 4 or 8, and wherein a CCE level of the PDCCHsignaling in the UESS is 4 or
 8. 4. The machine-readable storage mediumaccording to claim 1, wherein the first search space comprises a firstUE-specific search space (UESS) that is used to schedule a firstcomponent carrier (CC) of the UE, and wherein the second search spacecomprises a second UESS that is used to schedule a second CC of the UE.5. The machine-readable storage medium according to claim 1, wherein theinstructions to determine whether the first search space and the secondsearch space overlap in the at least one of the plurality of CCEsincludes instructions to: determine whether there is at least one CCE inthe plurality of CCEs whose index in the first search space is the sameas an index in the second search space, wherein the at least one CCEwhose index in the first search space is the same as the index in thesecond search space comprises the at least one of the plurality of CCEsover which the first search space overlaps the second search space. 6.The machine-readable storage medium according to claim 1, wherein theprogramming further includes instructions to: cease transmitting thePDCCH signaling excluding the CIF in the at least one of the pluralityof CCEs over which the first search space overlaps the second searchspace.
 7. A machine-readable storage medium having stored thereon,programming for execution by a machine, the programming includinginstructions to: receive PDCCH signaling from a base station, whereinthe PDCCH signaling is made up of at least one control channel element(CCE) of a first search space or a second search space, and wherein thefirst search space and the second search space comprise a plurality ofCCEs; and when the first search space and the second search spaceoverlap in at least one of the plurality of CCEs and when a length ofthe PDCCH signaling excluding a carrier indication field (CIF) in thefirst search space is equal to a length of PDCCH signaling including theCIF in the second search space, parse the received PDCCH signalingincluding the CIF that is positioned within the at least one of theplurality of CCEs over which the first search space overlaps the secondsearch space.
 8. The machine-readable storage medium according to claim7, wherein the first search space is a common search space (CSS), andthe second search space is a UE-specific search space (UESS).
 9. Themachine-readable storage medium according to claim 7, wherein theprogramming further includes instructions to: determine locations of thefirst search space and second search space; and determine whether thefirst search space and the second search space overlap in the at leastone of the plurality of CCEs.
 10. The machine-readable storage mediumaccording to claim 9, wherein the instructions to determine whether thefirst search space and the second search space overlap in the at leastone of the plurality of CCEs include instructions to: determine whetherthere is at least one CCE in the plurality of CCEs whose index in thefirst search space is the same as the index in the second search space,wherein the at least one CCE whose index in the first search space isthe same as the index in the second search space is the at least one ofthe plurality of CCEs over which the first search space overlaps thesecond search space.